Pseudophakic correction factors for optical biometry

INTRODUCTION: The IOLMaster of Carl Zeiss Jena, which has recently become available, is a combined instrument for biometry and intraocular lens (IOL) planning for cataract surgery utilizing partial coherence interferometry for measuring axial length. Whereas measurement data from classical ultrasound biometry, e.g. in pseudophakic eyes, need to be corrected by +0.4 to -0.8 mm--depending on the lens material--smaller corrections are expected to be necessary in optical biometry. Correction factors for various modern IOL materials were estimated theoretically and checked in first clinical measurements. METHODS: Starting from the dispersion relation of PMMA and manufacturers' phase refractive index data at 546 nm, the group refractive indices of different IOL materials were estimated for the IOLMaster wavelength of lambda=780 nm. Then, for an average eye of 23.48 mm, the center thicknesses of emmetropizing lenses of different material were calculated. Finally, comparing the pseudophakic optical axial lengths thus deduced with the respective phakic value, individual material-specific correction factors were obtained. RESULTS: Expressing the true axial length ALtrue by the length ALphak measured in phakic mode and a correction factor delta (ALtrue=Alphak+delta), we obtained values of delta=0.12+/-0.01 mm for all IOL materials considered (PMMA, silicone, collamer, AcrySof, MemoryLens). For aphakic eyes, delta=0.20 mm was deduced. DISCUSSION: The calculations suffered from the fact that hardly any information relating to optical material specifications of IOLs is available from lens manufacturers. Therefore, calculations had to be based on--nevertheless realistic--assumptions. Early clinical results support our theoretical findings. Thus, optical biometry seems to be more reliable and forgiving in pseudophakic eyes than classical ultrasound.     

Comparison of anterior chamber depth measurement methods in phakic and pseudophakic eyes

PURPOSE: To compare anterior chamber depth (ACD) measurements in phakic and pseudophakic eyes using a slit-beam photographic technique (IOLMaster, Carl Zeiss Meditec AG) with those obtained with the laboratory prototype version of partial coherence interferometry (PCI) and with conventional applanation ultrasound in phakic eyes. SETTING: Department of Ophthalmology, Vienna General Hospital, Vienna University, Vienna, Austria. METHODS: Thirty-three ACDs of 28 patients with age-related cataract were measured preoperatively with a slit-beam photographic technique (IOLMaster) and the prototype version of PCI. In 24 eyes, the ACD was also assessed with applanation ultrasound. In addition, 34 ACDs of 18 pseudophakic patients in a different study population were examined postoperatively with the IOLMaster and PCI. RESULTS: The median ACD in the phakic eyes was 3.06 mm (range 1.93 to 3.90 mm) with the IOLMaster, 3.09 mm with PCI (range 1.49 to 4.06 mm), and 2.87 mm (range 2.18 to 3.33 mm) with applanation ultrasound. The precision was 0.005 mm for PCI and 0.015 mm for IOLMaster measurement. The median difference between the IOLMaster and PCI ACD biometry was 0.01 mm +/- 0.14 (SD) (range -0.44 to 0.17 mm) (P =.71). In pseudophakic eyes, the 2 methods showed a median difference of -0.22 mm (range -0.45 to 1.99 mm) (P >.1) and did not correlate (r = 0.21; P >.2). CONCLUSIONS: In phakic eyes, the difference between IOLMaster and PCI measurements was small and not statistically significant. In pseudophakic eyes, the difference was larger and the methods did not correlate.     

Signal quality of biometry in silicone oil-filled eyes using partial coherence laser interferometry

PURPOSE: To assess the practical feasibility and signal quality of axial length measurements by partial coherence laser interferometry in silicone oil-filled eyes with previous complicated vitreoretinal surgery. SETTINGS: Department of Ophthalmology, University Cologne, Cologne, Germany. METHODS: Using a Zeiss IOLMaster, axial length measurements and signal-to-noise ratios of optical biometry in silicone oil-filled eyes (n=45) and contralateral eyes without tamponade (n=41) were analyzed. RESULTS: Axial length measurements with signal-to-noise ratio > or =2 were feasible in 41 of 45 silicone oil-filled eyes (91%) and 37 of 41 eyes without tamponade (90%). Cataract, central retinal detachment, vitreous hemorrhage, and emulsified oil droplets attached to the intraocular lens were reasons for failure of partial coherence laser interferometry. The signal-to-noise ratio of the first 2 measurements was significantly smaller (P=.04) in silicone-filled eyes (4.4 +/- 2.0) than in eyes without tamponade (5.5 +/- 3.0). Axial lengths of the oil-filled eye and the contralateral eye showed a significant intraindividual correlation (P<.0001, Spearman r=0.84). CONCLUSIONS: Partial coherence laser interferometry shows good clinical practicability in silicone oil-filled eyes with previous complicated vitreoretinal surgery. Further studies are needed to assess the reliability of these measurements with regard to postoperative refraction after combined oil removal and cataract surgery.     

IOL Master在硅油填充眼生物测量中的应用

目的评价IOL Master对硅油填充眼进行生物测量的准确性。方法前瞻性选取2008年1月至12月间在我院行硅油取出术的硅油填充眼患者29例（29只眼）,在术前、术后均用IOLMaster测量眼轴长度,并用A超测量术后的眼轴,对结果进行比较。结果有6只眼因晶状体混浊明显或不能固视而未能测得眼轴,其余患眼IOL Master测得的术前、术后眼轴长分别为（26.37±2.80）mm及（26.29±2.77）mm,差值为（-0.04±0.15）mm（-0.36～0.23mm）（P=0.239）,相关系数为0.999;A超测得的患眼术后眼轴长度为（26.06±2.80）mm,患眼术前IOL Master与术后A超测得眼轴长度的差值为（0.18±0.17）mm（-0.21～0.58mm）（P〈0.01）,相关系数为0.998;术后IOL Master与A超测得眼轴长度的差值为（-0.23±0.13）mm（-0.54～-0.05mm）（P〈0.01）,相关系数为0.999。结论 IOL Master光学生物测量法可对硅油填充眼进行准确可靠的生物测量。     

Accuracy of segmented measurement of axial length in ultra-high myopia filled with silicone oil using immersion B-scan ultrasonography

AIM: To evaluate the accuracy of segmented measurement of axial length (AL) in high myopia filled with silicone oil by immersion B-scan ultrasonography (immersion B-scan). METHODS: From June 2016 to June 2020, a total of 67 ultra-high myopia inpatients (67 eyes) who underwent silicone oil removal combined with cataract extraction and intraocular lens (IOL) implantation were retrospectively enrolled. The preoperative axial length (AL) of 31 patients with severe cataract were segmented measured using immersion B-scan (B-scan group) and another 36 patients with mild or moderate cataract were measured using IOLMaster 500 (IOLMaster group). The post-operative ALs in two groups were both measured using IOLMaster 500. The IOL power was calculated with Haigis formula. The differences in ALs between pre- and post-surgery, as well as the postoperative refractive spherical equivalent, absolute refractive error, the prediction deviation of postoperative refraction and best corrected visual acuity (BCVA) were compared. RESULTS: The pre- and post-operative ALs were 30.46±1.63 mm (range 28.09-33.51 mm) and 30.42±1.70 mm (range 28.03-33.90 mm) in B-scan group (t=0.644, P=0.542) and 30.51±1.21 mm (range 28.03-33.90 mm) and 30.43±1.27mm (range 28.54-33.50 mm) in IOLMaster group (t=1.843, P=0.074), respectively. Three months after surgery, BCVA were 0.45±0.13 (range 0.3-0.9) and 0.44±0.20 (range 0.2-1.0) in B-scan and IOLMaster group respectively (t=0.086, P=0.932). There was no significant difference of the postoperative spherical equivalent (-3.11±0.65 D vs -3.21±0.51 D, t=0.671, P=0.505) and the absolute refractive error (0.589±0.340 vs 0.470±0.245 D, t=1.615, P=0.112) between two groups. In B-scan group, absolute refractive error within ±0.50 D was found in 18 eyes (58.1%), within ±1.00 D in 26 eyes (83.9%), and within ±1.50 D in 31 eyes (100%). In IOLMaster group, absolute refractive error within ±0.50 D was found in 23 eyes (63.9%), within ±1.00 D in 34 eyes (94.4%), and within ±1.50 D in 36 eyes (Z=0.757, P=0.449). CONCLUSION: The segmented measurement of ALs by immersion B-scan shows comparable measurement accuracy with that of IOLMaster 500 in ultra-high myopia patients with severe cataract secondary to silicone oil filling and can obtain an ideal postoperative refractive state.     

黏度5500 mPas硅油填充眼超声生物学测量的准确性

背景 硅油填充眼超声生物学测量的准确性和可行性是眼科诊疗过程中的难题,对硅油眼性白内障行超声乳化联合人工晶状体(IOL)植入术时IOL度数的计算造成困难.一些大型医院常采用光学测量仪IOLMaster实现对硅油填充眼的生物学测量,但其对屈光介质严重混浊的病例仍无法进行测量.曾有研究者采用超声改良法或眼轴分段测量法进行估算,但其研究结果可能由于硅油黏度的不同而差异较大.目的 探讨超声对黏度5 500 mPas硅油填充眼生物学测量的计算方法,为超声法对不同黏度硅油填充眼进行生物学测量提供方法学参考依据. 方法 采用B型超声仪于37℃下对高度分别为20、24和28 mm的平衡盐溶液进行测量,并与黏度5 500 mPas硅油的相应测量高度进行比较,以得到计算硅油眼实际眼轴长度(AL)的公式.收集于2012年5月至2014年3月在青岛市海慈医疗集团接受黏度为5 500mPas硅油填充治疗的复杂性视网膜疾病患者30例32眼,按实际AL分为AL＜26 mm组(16例18眼)和AL≥26 mm组(14例14眼),分别于硅油取出术前1d行B型超声、IOL Master测量AL,并于术后3个月用A型超声及B型超声测量AL.对不同方法测量的AL值进行差异比较和相关分析,并对手术前后受检眼玻璃体腔长度和屈光度进行比较.结果 B型超声波在黏度5 500 mPas硅油中的传播速度为1 023 m/s,超声波在硅油眼与正常玻璃体腔中测算AL的校正系数为0.668,校正AL=角膜顶点至晶状体后极或囊膜中央点距离+0.668×晶状体后极或囊膜中央点至黄斑距离.AL＜26 mm组和AL≥26 mm组受检眼用术前B型超声校正公式法、IOLMaster测量法、术后A型超声测量法和术后B型超声测量法测量的AL值的总体比较,差异均无统计学意义(F=0.108,P=0.955;F=0.011,P=0.998);硅油取出术前,B型超声校正公式法测量的AL值与IOLMaster测量法、术后B型超声测量法和术后A型超声测量法间测得的AL值均呈明显正相关(AL＜26 mm组:r=0.876、0.921、0.809,均P＜0.01;AL≥26 mm组:r=0.943、0.956、0.955,均P＜0.01).硅油取出术前1d,B型超声测量的玻璃体腔长度校正值为(20.78±2.13)mm,硅油取出术后3个月测量的玻璃体腔实际长度为(20.89±2.16) mm,二者间差异无统计学意义(t=0.795,P=0.219).受检眼中16眼行IOL植入术后平均屈光度为(-1.25±1.69)D,与术前保留的(-1.50±0.00)D比较,差异无统计学意义(t=0.585,P=0.284).结论 B型超声法对硅油填充眼的生物学测量准确、简便,用于临床的可行性较好.     

不同测量仪器和不同IOL屈光度计算公式对硅油填充合并白内障眼IOL屈光度测算的比较

背景 玻璃体切割联合硅油填充眼易诱发和加速白内障的形成,白内障联合硅油取出术前人工晶状体(IOL)屈光度的准确测算是术眼获得术后良好视觉质量的关键. 目的 研究不同仪器和不同IOL计算公式在硅油填充合并白内障眼行白内障摘出联合IOL植入术前IOL屈光度测算的差异,并测算术前预测IOL屈光度与术后术眼屈光度的误差,为临床相关工作提供参考依据. 方法 采用前瞻性非随机对照的研究方法,于2011年8月至2013年10月在苏州大学附属第二医院连续纳入玻璃体切 割术后硅油填充合并白内障者36例36眼,患眼均于硅油乳化后4个月～2年拟行白内障超声乳化+IOL植入+硅油取出术,术前分别用IOLMaster及A型超声联合手动角膜曲率计(MK)测量术眼眼轴长度(AL)、角膜曲率(CC)和前房深度(ACD)等生物学参数,分别采用SRK-Ⅱ、SRK/T、Hoffer Q、Holladay 1和Haigis计算公式和预留的屈光度计算拟植入的IOL屈光度,分析和比较IOLMaster及A型超声联合MK用上述计算公式测算的IOL理论屈光度值与术后术眼实际屈光度值的平均预测误差(MPE)和平均绝对屈光误差(MAE). 结果 A型超声+MK和IOLMaster测得的AL分别为(25.21±1.02) mm和(25.43±0.90) mm,ACD分别为(3.07±0.62) mm和(3.22±0.38)mm,A型超声+MK测量的AL和ACD值明显小于IOLMaster测量结果,差异均有统计学意义(均P=0.000).IOLMaster与A型超声+MK测得的CC分别为(44.58±1.57)D和(44.56±1.62)D,差异无统计学意义(P=0.568).用IOLMaster测量时,SRK/T公式的MAE明显小于SRK-Ⅱ、Hoffer Q、Holladay 1和Haigis公式的MAE,差异均有统计学差异(P=0.017、0.009、0.012、0.001);Haigis公式的MAE明显大于SRK-Ⅱ、HofferQ和Holladay 1公式的MAE,差异均有统计学意义(P=0.026、0.035、0.021).用A型超声+MK测量时,Haigis公式的MAE明显大于与SRK-Ⅱ、SRK/T、Hoffer Q和Holladay 1公式的MAE,差异均有统计学意义(P=0.007、0.004、0.018、0.006).用SRK-Ⅱ、SRK/T、Hoffer Q和Holladay 1公式计算时,IOLMaster与A型超声+MK间测量的MAE≤1.0D眼数比较差异均无统计学意义(x2=0.107、2.250、0.845、0.084,均P＞0.05);用Haigis公式计算时,IOLMaster测量的MAE≤1.0D眼数明显多于A型超声+MK测量结果,差异有统计学意义(x2=4.431,P=0.035). 结论 使用IOLMaster时SRK/T公式测算的IOL屈光度准确性最高,用A型超声+MK测量时推荐使用SRK-Ⅱ、SRK/T、Hoffer Q和Holladay 1测算公式.     

硅油填充手术后继发性青光眼的临床观察

目的 探讨硅油填充手术后继发性青光眼(SOG)的危险因素和治疗方法.方法 玻璃体切割手术同时眼内硅油填充的93例患者95只眼纳入本研究.其中,手术中保留晶状体37只眼,摘除晶状体58只眼;摘除晶状体眼中,植入人工晶状体10只眼.硅油填充时间≤6个月者32只眼,＞6个月者63只眼.手术后1、2周,1个月时复查眼底和眼压,均随访至硅油取出.随访时间2～25个月,平均随访时间(9.5±5.1)个月.手术后1个月眼压高于21 mm Hg(1 mm Hg=0.133 kPa),同时排除有明显原发因素及新生血管性青光眼等其他继发因素所引起的眼压升高者诊断为SOG.SOG确诊后,立刻给予盐酸卡替洛尔、布林佐胺滴眼液、甘露醇静脉滴注降眼压治疗,治疗1周眼压仍不能降至正常者行硅油取出手术,仍不能降至正常者行小梁切除手术.结果 21只眼发生SOG,占总眼数的22.1%.21只眼的平均硅油填充时间为(10.8±5.1)个月.其中,16只眼为无晶状体眼,占无晶状体眼的33.3%;5只眼为有晶状体眼或人工晶状体眼,占有晶状体眼或人工晶状体眼的10.6%.18只眼的硅油填充时间＞6个月,占硅油填充时间＞6个月眼的28.6%;3只眼的硅油填充时间≤6个月,占硅油填充时间≤6个月眼的9.4%.17只眼查见硅油乳化,占81.0%.行硅油取出手术后17只眼1周内眼压恢复正常,占SOG眼的81.0%.结论 无晶状体眼、硅油填充时间长是SOG发病的危险因素,硅油乳化是主要的发病原因,及时取出硅油是有效的治疗方法.

Abstract：

Objective To investigate the risk factors and treatment of silicone oil glaucoma (SOG).Methods Ninety-five eyes of 93 patients who underwent pars plana vitrectomy and silicone oil tamponade were evaluated in this study. The lens was removed in 58 eyes in which intraocular lens (IOL) was implanted in 10 eyes, so 48 eyes were aphakic. Silicone oil tamponade time was ≤6 months in 32 eyes,and ＞6 months in 63 eyes. The follow-up time ranged from 2 to 25 months, with a mean of (9.5±5.1)months. The fundus and intraocular pressure (IOP) were evaluated at 1 week, 2 weeks and 1 month after surgery. The diagnosis of SOG was established if the one-month postoperative IOP ＞ 21 mm Hg (1 mm Hg=0.133 kPa), and primary and neovascular glaucoma were excluded. After the diagnosis of SOG, carteolol hydrochloride and brinzolamide solution were immediately applied to the eye, and intravenous mannitol infusion was performed. If the IOP still can not be controlled after 1 week of such treatment, silicone oil removal surgery will be performed. If removal of silicone oil can not control the IOP,trabeculectomy surgery will be performed. Results SOG occurred in 21 eyes (22.1%), including 5 phakic eyes (10.6% of 47 phakic eyes) and 16 aphakic eyes (33.3% of 48 aphakic eyes) , 3 eyes (9.4% of 32 eyes)with short tamponade time (≤6 months) and 18 eyes (28.6% of 63 eyes) with long tamponade time (＞6months). The average silicone oil tamponade time was (10.8±5.1) months. Emulsification of the silicone oil occurred in 17 eyes (81.0%). After silicone oil removed, IOP was controlled in 17 eyes (81.0%) within one week. Conclusions Aphakic eye and the duration of silicone oil tamponade are the risk factors of SOG.Emulsification of silicone oil is the main cause. Silicone oil removal is an effective way to treat SOG.     

Evaluation of the practicality of optical biometry and applanation ultrasound in 253 eyes

PURPOSE: To evaluate the percentage of eyes that could not be measured using optical biometry and ultrasound applanation and the reasons. SETTING: Department of Ophthalmology, Johannes Gutenberg-University Hospital, Mainz, Germany. METHODS: Optical biometry (IOLMaster, Carl Zeiss Meditec AG) and A-scan ultrasound biometry were performed consecutively in 253 eyes scheduled for cataract surgery the next day. Lens opacities were evaluated with the Opacity Lensmeter (Interzeag), and a slitlamp examination and measurement of visual acuity were performed. The 2 techniques were compared in terms of the rate of and reasons for primary measurement failure. RESULTS: Measurement with the IOLMaster was not possible in 44 eyes (17%). Failed measurements were the result of a combination of low visual acuity and lens opacity in 45% of eyes, posterior subcapsular opacity in 25%, and macular disease in 7%. Measurement with ultrasound biometry was not possible in 10 eyes (4%); 7 eyes were filled with silicone oil and in 3 cases, the patient refused biometry. CONCLUSIONS: Optical biometry allowed comfortable, noncontact, high-precision measurement in the optical axis. Uncorrected visual acuity and lens opacity were predictors of successful measurements. Eyes with dense cataract or poor visual acuity are better evaluated using ultrasound applanation.     

硅油眼的硅油取出联合白内障超声乳化术的疗效观察

目的观察玻璃体切除术后硅油填充眼患者硅油取出联合超声乳化人工晶状体植入术的术后视力、屈光度变化和术中及术后并发症情况。方法收集17例(17眼)玻璃体切除术后硅油填充眼的白内障患者,行硅油取出联合超声乳化人工晶状体植入术,观察术前及术后最佳矫正视力(BCVA)、眼压,术中及术后并发症情况,并对术后实际屈光度和术前目标屈光度进行比较。结果随访时间为3～14.5个月,平均(4.00±2.81)个月。6眼术后BCVA为0.05～0.1,6眼为0.12～0.3,4眼为0.4～0.7,1眼>0.8。术后眼压为(13.61±3.67)mm Hg(1mm Hg=0.133kPa),与术前(16.31±6.95)mm Hg相比,差异无统计学意义(Z=1.1043,P=0.2933)。术后实际测得屈光度为(-1.09±3.91)D,与术前目标屈光度(-1.46±1.29)D相比,差异无统计学意义(Z=3.7504,P=0.0527)。术中1眼出现灌注偏离综合征,9眼行中央部后囊膜切除,所有患者术中未出现晶状体坠入玻璃体腔等并发症。术后早期5眼出现轻度角膜水肿,1眼行掺钕钇铝石榴石(Nd:YAG)激光后囊膜切开,2眼发生视网膜再次脱离。结论玻璃体切除硅油填充患者行硅油取出联合超声乳化人工晶状体植入术可有效提高视力,术后实际屈光度与术前目标屈光度较为一致,手术并发症少,手术方法安全、有效。     

Intraoperative biometry for intraocular lens (IOL) power calculation at silicone oil removal

PURPOSE: Cataract development is common following retinal detachment surgery that necessitates silicone oil injection. Intraocular lens (IOL) power calculation in the presence of silicone oil is challenging for many reasons. The authors evaluated the accuracy of intraoperative biometry during cataract surgery in silicone-filled eyes. METHODS: Twelve cases of cataract in eyes filled with silicone oil after retinal detachment surgery were included. Preoperatively, keratometric readings were documented. Intraoperative axial length was measured following removal of silicone oil using a sterile probe of the Nidek Echoscan US800 unit. IOL power calculation was computed using the SRK/T formula. This was followed by phacoemulsification and foldable lens implantation. Postoperative refraction allowed evaluation of the accuracy of intraoperative biometry. The predictability of three different formulas was also compared (Holladay, SRK/T, and SRK II). RESULTS: Seven men and five women with a mean age of 50.2 years were included in the study. The mean postoperative spherical equivalent using the described technique was 6.77 +/- 0.43 diopters. SRK/T and Holladay formula had the best predictability for high axial length eyes, whereas the three studied formulas showed no significant differences in predictability in eyes with normal axial length. CONCLUSIONS: Intraoperative biometry proved to have good predictability for the absolute postoperative refractive error in cataract surgery for eyes at the time of silicone oil removal. This predictability was accurate independent of axial length.     

Correlation between quantity of silicone oil emulsified in the anterior chamber and high pressure in vitrectomized eyes

PURPOSE: To assess the existence of any correlation between the quantity of silicone oil emulsified in the anterior chamber and the incidence of high intraocular pressure in vitrectomized eyes. METHODS: Forty-nine eyes of 49 patients underwent vitrectomy with silicone oil injection as an adjuvant procedure. At the time of observation, between September 1999 and September 2000, 13 eyes (26.5%) were phakic; 23 eyes (47%) were pseudophakic; and 13 eyes (26.5%) were aphakic. Ultrasound biomicroscopy, slit-lamp biomicroscopy, and gonioscopy were performed to quantify the presence of silicone oil emulsified in the anterior chamber. RESULTS: The 13 phakic eyes did not have a high intraocular pressure. In 8 of the 13 eyes, ultrasound biomicroscopy detected only scarce oil emulsification in the anterior chamber (0.304 mm); in 5 of the 13 eyes, gonioscopy and ultrasound biomicroscopy did not detect anterior chamber oil emulsification. Fourteen of 23 pseudophakic eyes had a high intraocular pressure; of these, ultrasound biomicroscopy detected an abundant amount of anterior chamber oil emulsification (0.922 mm). Nine of 23 pseudophakic eyes did not have a high intraocular pressure; of these, ultrasound biomicroscopy detected little anterior chamber oil emulsification (0.209 mm). The 13 aphakic eyes had a high intraocular pressure; of these, ultrasound biomicroscopy detected an abundant amount of anterior chamber oil emulsification (0.795 mm). The coefficient of correlation for the measurements obtained was 0.98 (F = 62.3, P = 0.05; t = 11.1, P = 0.001). CONCLUSION: This study showed a high correlation between the incidence of high intraocular pressure and the quantity of emulsified silicone oil in the anterior chamber.     

Refractive outcome of silicone oil removal and intraocular lens implantation using laser interferometry

PURPOSE: To evaluate the refractive outcome of silicone oil removal and intraocular lens (IOL) implantation using laser interferometry. METHODS: Thirteen silicone oil-filled eyes of 12 patients were included in the study. IOL power calculation was performed using laser interferometry (IOLMaster V1.1; Carl Zeiss, Jena, Germany). All of these eyes underwent silicone oil removal and cataract extraction with IOL implantation. Post-operative refraction was evaluated. RESULTS: The mean deviation of the final post-operative refraction (spherical equivalent) was -0.30+/-0.91 D (range, -1.87 to +1.3) at 12 weeks. The mean axial length of the eyes was 22.99+/-0.84 mm (range, 22.07-25.24 mm). No major complications occurred intra- or post-operatively. CONCLUSION: Laser interferometry appears to be a feasible and satisfactorily accurate method to calculate IOL power in some silicone oil-filled eyes. Further studies comparing this technique to others are warranted.     

IOLMaster与A型超声校正法测量硅油眼眼轴的对照研究

背景白内障摘出联合人工晶状体（IOL）植入术是提高患者生活质量的方法,但传统的硅油眼IOL度数的测量往往较实际的度数偏大。光学相干生物测量技术已被广泛用于IOL度数的测量,但需要探求其所测IOL度数与实际值的差别。目的探讨并比较IOLMaster及眼部A型超声生物测量校正方法测量硅油填充眼眼轴的准确性,以及2种测量方法在计算IOL度数方面的差别。方法42例44只硅油填充眼按眼压不同分为≥10mmHg组29眼和〈10mmHg组15眼,分别用IOLMaster和眼部A型超声测量校正2种方法在硅油取出术前和术后测量眼轴,利用术前测量的眼轴及角膜曲率推算理论IOL度数,评价IOLMaster测量硅油填充眼眼轴的优点及其预测IOL度数的临床意义。结果对于眼压≥10mmHg的硅油填充眼,IOLMaster测量法与A型超声校正法所得眼轴数值之间差异有统计学意义（P=0．015）,但硅油取出术后与术前眼轴差异无统计学意义（P=0．10）,IOLMaster测量硅油眼眼轴的误差值均低于A型超声法,差异有统计学意义（ZMIOLMaster参照=一2．236,P=0．025）,而且关于预测的IOL度数误差,IOLMaster测量法也小于A型超声校正法;对于〈10mmHg的硅油填充眼,IOLMaster和A型超声校正法在硅油取出术后所测的眼轴和IOL度数均明显低于硅油取出前所测值,差异均有统计学意义（P=0．006）。结论眼压稳定、眼底情况较好的硅油眼行硅油取出联合IOL植入术前采用IOLMaster测量法预测IOL度数的准确性和稳定性优于A型超声校正法,但对于术前眼底情况复杂、手术次数多、眼压不稳定的硅油眼,2种方法均无法准确预测术后眼轴及IOL度数,建议硅油取出后再行IOL植入术。     

Cataract surgery in eyes after vitrectomy filled with long-term silicone oil tamponade

PURPOSE: Evaluation of the results of cataract extraction in eyes filled with silicone oil. MATERIAL AND METHODS: Twenty-nine eyes of 29 patients underwent cataract extraction without intraocular lens implantation, in eyes after vitrectomy filled with silicone oil. The average time of silicone oil tamponade was 3.5 years (range from 10 months to 6 years). The mean follow-up was 26.1 +/- 17.5 months. RESULTS: Useful visual acuity was achieved in 55% eyes. The main complication was the increased intraocular pressure, which appeared in 38% eyes. CONCLUSION: Cataract surgery in eyes with long-term silicone oil tamponade get benefit, because it enables restoring the useful visual acuity. More advanced retinal pathology and silicone oil tamponade increase the number of complications.     

Refractive changes in silicone oil-filled pseudophakic eyes

PURPOSE: We examined the refractive changes in pseudophakic eyes of patients with idiopathic macular hole treated with silicone oil injection. METHODS: Twenty consecutive eyes of 19 patients with idiopathic macular hole who had undergone successful pars plana vitrectomy using silicone oil tamponade were studied retrospectively. Lensectomy with intraocular lens (IOL) implantation was performed on each patient before vitreous surgery. Five biconvex type IOL models were used. After pars plana vitrectomy and fluid-air exchange, silicone oil was injected to replace the air completely. Macular hole closure was confirmed by optical coherence tomography, and silicone oil removal was performed. Manifest refractions before silicone oil filling, with silicone oil filling, and after silicone oil removal were determined. RESULTS: A mean hyperopic shift +/- SD in spherical equivalents of +5.69 +/- 1.71 diopters (P < 0.0001) was observed with silicone oil instillation. In contrast, a mean myopic shift +/- SD of -5.63 +/- 1.33 diopters was observed after silicone oil removal (P < 0.0001). The absolute value of the refractive shift showed a strong correlation with the posterior radius of the IOL (r = 0.699, P < 0.0001). CONCLUSION: IOL models with steeper posterior convex curvature result in larger refractive deviations in patients scheduled for silicone oil instillation.     

Pr?zision eines neuen Biometrieger?ts zur Messung pseudophaker Augen

Background

Biometric measurements and the knowledge of interrelationships of structures within the eye are especially mandatory for cataract and refractive surgery. As the number of pseudophakic patients steadily increases because cataract surgery becomes more easily available all over the world, exact biometry of eyes with crystalline lenses as well as pseudophakic eyes is gaining interest. In the present study we compared biometric measurements in pseudophakic eyes using a new optical low-coherence reflectometry (OLCR) device with results measured by the IOLMaster.

Patients and methods

In this prospective study 140 pseudophakic eyes from 123 adult volunteers following uneventful cataract surgery and IOL implantation were examined at the International Vision Correction Research Centre (IVCRC) at the University of Heidelberg, Germany. The aim of this study was to evaluate a functional prototype of the new LENSTAR LS 900 (Haag-Streit)/ALLEGRO BioGraph (Wavelight) biometer and the IOLMaster V.5 (Carl Zeiss Meditec) and to compare axial length (AL) and keratometry measurements with those obtained by the IOLMaster. Additionally we investigated whether the LENSTAR/BioGraph can detect anterior chamber depth (ACD) and the effective lens position (ELP) of IOLs by OLCR in pseudophakic eyes. Patients with corneal or intraocular pathology and patients who had undergone other surgery in the investigated eye or whose cataract surgery dated back less than 4 weeks were not included in the study. Measurements were repeated with both devices as recommended by the manufacturers. Results were compared using Bland-Altman plots, Passing Bablok regression analysis and Pearson correlation calculations (MedCalc version 7.3.0.1).

Results

Valid axial length measurements were available in 137 eyes. The mean values were 23.75?mm for both devices (SD±2.08 with the IOLMaster, ±1.7 with the LENSTAR/BioGraph). The mean corneal radius (R) was 7.7±0.27?mm (IOLMaster) vs. 7.74±0.29?mm (LENSTAR/BioGraph). Valid ACD measurements with the LENSTAR/BioGraph were achieved in 30% of all cases. In 98.6% of the eyes in which ACD was analyzed manually a mean ACD of 4.73±0.53?mm was found.

Conclusions

Both devices tested in this study showed a high correlation for AL and keratometry measurements. ACD measurements performed with the LENSTAR/BioGraph showed a measurable signal but the prototype calculated a value only in the minority (30%) of cases. This study showed that on the one hand the LENSTAR/BioGraph has the potential to be a reliable and useful machine for clinical everyday routine: This space and time-saving device includes several features which make it a patient and user friendly tool for diagnostics as well as screening. On the other hand we found that the software used in the prototype could be improved especially in order to identify IOLs and to measure reliable ACD values in pseudophakic patients. IOL surfaces did not generate sufficient interference signals in the LENSTAR/BioGraph and although the light reflected by the IOL surfaces was recognized by the device the software version used in this study did not generate numerical results for ACD.     

IOL-Master测量硅油填充眼屈光结果分析

目的评价IOL—Master测量硅油填充眼屈光度数的准确性并分析不同因素与术后屈光误差的关系。方法29例（29眼）硅油填充眼行硅油取出联合人工晶状体（IOL）植入术,术前用IOL—Master进行IOL测量。根据不同病因、硅油放置时间、眼轴、术后并发症等因素进行分类,研究术后视力恢复情况及测量误差产生的原因。结果术后视力较术前均有不同程度的提高,屈光度数的平均预测误差为0．329±0．846（-1．5～-2．0D）,眼轴长度（P〉0．05）、病因[裂孔源性（t=0．478,P=0．637）、黄斑裂孔（t=0．135,P=0．895）]、是否近视（t=0．435,P=0．667）与术后产生的屈光误差均无相关性,硅油存留时间〈1年者术后矫正视力恢复好。结论硅油填充眼患者采用硅油取出联合IOL植入术对视力有一定提高,IOL—Master测量硅油填充眼IOL度数是相对准确、安全、方便的方式。     

Agreement analysis of LENSTAR with other techniques of biometry

Purpose

To assess the agreement of the optical low-coherence reflectometry (OLCR) device LENSTAR LS900 with partial coherence interferometry (PCI) device IOLMaster and applanation and immersion ultrasound biometry.

Methods

We conducted the study at the Ophthalmology Clinic, University of Malaya Medical Center, Malaysia. Phakic eyes of 76 consecutive cataract patients were measured using four different methods: IOLMaster, LENSTAR and A-scan applanation and immersion ultrasound biometry. We assessed the method agreement in the LENSTAR-IOLMaster, LENSTAR-applanation, and LENSTAR-immersion comparisons for axial length (AL) and intraocular lens (IOL) power using Bland–Altman plots. For average K, we compared LENSTAR with IOLMaster and the TOPCON KR-8100 autorefractor-keratometer. SRK/T formula was used to compute IOL power, with emmetropia as the target refractive outcome.

Results

For all the variables studied, LENSTAR agreement with IOLMaster is strongest, followed by those with immersion and applanation. For the LENSTAR-IOLMaster comparison, the estimated proportion of differences falling within 0.33 mm from zero AL and within 1D from zero IOL power is 100%. The estimated proportion of differences falling within 0.5 D from zero average K is almost 100% in the LENSTAR-IOLMaster comparison but 88% in the LENSTAR-TOPCON comparison. The proportion of differences falling within 0.10 mm (AL) and within 1D (IOL power) in the LENSTAR-IOLMaster comparison has practically significant discrepancy with that of LENSTAR-applanation and LENSTAR-immersion comparisons.

Conclusions

In phakic eyes of cataract patients, measurements of AL, average K, and IOL power calculated using the SRK/T formula from LENSTAR are biometrically equivalent to those from IOLMaster, but not with those from applanation and immersion ultrasound biometry.     

Biometry of the silicone oil-filled eye: II

PURPOSE: In phakic silicone oil-filled eyes, removal of the silicone oil can be combined with phacoemulsification and intraocular lens (IOL) implantation. True axial length (AL) of the silicone oil-filled (viscosity 1300 centistokes) eye can be estimated from the measured AL (MAL) obtained on A and/or B scan echography, by multiplying MAL by a conversion factor of 0.71. IOL power can then be calculated using current biometry formulae (SRK/T). This study aims to evaluate the conversion factor in clinical practice. METHODS: Eleven patients undergoing combined removal of silicone oil and phacoemulsification with IOL implant were studied. Patients were divided into two groups. In Group 1 (seven patients), the IOL was placed in the capsular bag and in Group 2 (four patients) the IOL was placed in the ciliary sulcus. Calculated AL (CAL) was obtained by multiplying the MAL of the silicone oil-filled eye (as measured on A or B scan ultrasonagraphy) by the conversion factor of 0.71. IOL power was then estimated using the CAL in the SRK/T formula. The spherical equivalent of the postoperative refractive error was compared to predicted refractive error. RESULTS: The mean difference in actual and predicted refractive error was 0.74 dioptres (D) (standard deviation 0.75 D) for Group 1 and 1.31 D (standard deviation 1.4 D) for Group 2. CONCLUSIONS: The conversion factor of 0.71 corrects for the apparent increase in AL induced by silicone oil of viscosity 1300 centistokes. This allows accurate prediction of the required IOL power in eyes undergoing combined cataract extraction, removal of silicone oil and lens implant. Sulcus placement of the IOL gives a less predictable result than placement in the capsular bag.